Children with severe disorders of speech who use assistive communication devices become dependent upon their sensory-motor abilities to activate buttons or sensors on their devices. If such children also have deficits in the skilled use of their limbs, then their communication abilities are further limited. We propose to measure the components of upper extremity motor function that relate directly to information and communication rate. We hypothesize that motor disability is an important contributor to decreased communication rate, and communication rate can be improved if the number and spacing of buttons on a communication device are modified to reflect the child's information transfer abilities. [unreadable] To test this, we propose the following specific aims: 1. Measure the time required to contact different numbers of buttons of different sizes in 10 children age 6-18 years with severe disorders of verbal communication and impairments of arm movement. The data will be analyzed in terms of information rate according to Fitts' Law and Hicks' Law, and the optimal spacing and number of buttons will be calculated for each child. The contribution of movement time and reaction time to information rate will be compared to performance on the Melbourne test of upper extremity function. The information rate will also be compared to the performance of 20 control subjects of similar ages. 2. Design a touch-screen computer interface that is optimized for the measured movements of each child with impairment, and compare the child's performance on the interface to their current device using a sequence of words randomly selected according to the statistics of the child's actual vocabulary. Compare the communication rate on the two devices to the maximum motor information rate predicted from specific aim 1 to determine the contribution of the motor impairment to overall communication ability. [unreadable] If these experiments are successful, they will generate important pilot data for assessing the effect of separate elements of motor disorders on communication, and they will provide a new methodology for the design of communication interface devices for individual children with severe speech and motor impairments. [unreadable] [unreadable]